Mix together the two types of flour with the poppy seeds, mustard seeds and the salt and form a well in the middle.
Cut the butter into pieces and place in the middle of the well, while still nice and cold. Knead together until you get a breadcrumb-like mixture, add the egg and a few spoonfuls of cold sparkling water. Knead quickly until you get a soft and even dough. Leave to stand in the fridge for at least 30 minutes, covered in cling film.
Roll out the dough using a rolling pin to around 5 mm in thickness and cover the slightly greased tart tin.
Peel the aubergine and cut into pieces. Clean the spring onions, chop finely and allow them to sweat in a pan with 2 tablespoons of oil and a ladle of water. After 10 minutes, add the pieces of aubergine, season with salt and pepper and cook. Leave to cool.
Beat together the eggs with the cream and add the ricotta and the diced Taleggio cheese
. Season with salt and pepper.
Add the aubergine and spring onion mixture, mix carefully and pour over the pastry base. Bake in the oven at 180°C for approximately 20-25 minutes.
Serve the tart warm.